1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member, and an electrophotographic apparatus and a process cartridge each including the electrophotographic photosensitive member.
2. Description of the Related Art
Technologies for improving the material, physical properties, and the like of the surface of the electrophotographic photosensitive member (photosensitive member) containing an organic photoconductive substance have been investigated in order that the durability of the electrophotographic photosensitive member may be improved.
However, the improvement of the durability of the electrophotographic photosensitive member tends to be liable to cause image deletion or electric potential variation.
The image deletion is considered to be caused by: the deterioration of a material in the surface layer of the electrophotographic photosensitive member due to, for example, ozone or a nitrogen oxide produced by charging of the electrophotographic photosensitive member; or the reduction in surface resistance of the surface layer due to the adsorption of moisture to the surface of the electrophotographic photosensitive member. The image deletion is liable to remarkably occur particularly under a high-temperature and high-humidity environment.
Similarly, the electric potential variation is liable to occur owing to the deterioration of a constituent material caused by repeated use of the electrophotographic photosensitive member.
Japanese Patent Application Laid-Open No. H08-272126 and Japanese Patent Application Laid-Open No. 2001-242656 each describe that the gas permeability and ozone resistance of the electrophotographic photosensitive member are improved, and the image density variation thereof is alleviated, by incorporating a specific additive into the electrophotographic photosensitive member.
Japanese Patent Application Laid-Open No. 2007-279446 describes that the incorporation of a specific additive into a photosensitive layer can improve the stability of electrical characteristics and hence suppresses the occurrence of an image failure such as a memory.
In recent years, an improvement in durability of an electrophotographic apparatus has been progressed, and hence a demand for additional alleviation of the image deletion and the electric potential variation has been growing.